Public feeling tracked on Twitter during Japan quake

Last week, we revealed how accurately Twitter posts reflect stock market sentiment. Now, six months after the 11 March megaquake and tsunami hit Japan's north-east coast, researchers are reporting similar strong correlations between tweets and the events associated with the disaster, showing in stark numbers how the social network can help authorities track how people are coping with sudden adversity.

Writing in a paper posted on 8 September on arxiv.org, Nigel Collier and colleagues from the National Institute of Informatics in Tokyo say they analysed 1.6 million local tweets written in Japanese and 49,000 written in English that were posted between 9 March and 31 May. They sought tweets with keywords covering three factors: the effects of the quake and tsunami, radiation hazards from swamped and/or severely jolted nuclear power stations and on general "public anxiety".

They found that alarmed tweets closely followed each disaster event, especially the initial shock, aftershocks and the tsunami, creating a powerful event tracking timeline for the authorities. "There was close correspondence been Twitter data and earthquake events," they report. Radiation-fear-related tweets showed Japanese speakers were worried sooner than English speakers as the Fukushima scenario played out. Anxiety levels shot up, as expected, but dropped back to pre-disaster levels sooner than expected.

"The results reveal that tweets in the native language play an important role in early warning in terms of their volume and timeliness," the researchers conclude. "Strong correlation between Twitter and public health events leads us to believe that Twitter data can be a useful resource in an early warning surveillance systems as well as a tool for analysing public anxiety and needs during times of disaster".